Melioidosis in Horses

Melioidosis is an uncommon bacterial infection of humans and animals. The disease-causing agent is Burkholderia pseudomallei, which occurs in the soil throughout southeast Asia, northern Australia, and the South Pacific. The disease has also occurred in humans in the US. Outbreaks have coincided with heavy rainfall and flooding and are associated with high humidity or temperature. Major excavations and disturbances in plumbing resulting in contamination of water supplies have also led to outbreaks. Animals become infected through inhalation, contamination of wounds, or ingestion.

Melioidosis has been diagnosed in many animals, including horses. In horses, signs may be similar to those of glanders, although infection without signs is common. The disease may be associated with single or multiple curd-like nodules or abscesses, which can be located in any organ. When the infection enters through the skin, it often develops at distant sites without evidence of active infection at the site of entry. Central nervous system disease has been seen in horses. Pneumonia is the most common form of disease caused by the bacteria in animals and humans. Lameness can occur. It is possible for an infection to lie dormant before becoming apparent. Death may occur in sudden and intense infections or when vital organs are affected.

Treatment can be expensive and prolonged. It is often unsuccessful and there is a risk that signs will return after treatment is discontinued. There is a possibility that this disease involves suppression of the immune system, especially in species that are less susceptible to infection. Treatment regimens using guidelines for human melioidosis include antibiotics. In areas where the bacteria are common, preventive measures such as minimizing environmental contamination by diseased animals and providing clean (chlorinated and filtered) drinking water may be helpful.